Method for forming polycrystalline thin film and method for fabricating thin-film transistor

A method for forming a polycrystalline semiconductor thin film comprising the steps of:

• forming a semiconductor thin film partially containing microcrystals serving as crystal nuclei for polycrystallization on an insulating substrate, comprising the steps of;
• forming an amorphous semiconductor layer, and
• annealing the amorphous semiconductor layer by a laser beam having an energy density near a threshold value of crystallization, thereby forming the microcrystal nuclei;
• polycrystallizing the semiconductor thin film by laser annealing,
• wherein the semiconductor thin film prior to being subjected to the polycrystallization process comprises:
• a microcrystalline semiconductor layer formed on the insulating substrate, which contains the microcrystals;
• and
• an amorphous semiconductor layer formed on the microcrystalline semiconductor layer so that the microcrystalline semiconductor layer is interposed between the insulating substrate and the amorphous semiconductor layer, and the microcrystalline semiconductor layer lies beneath the entire amorphous semiconductor layer.

A method for fabricating a thin-film transistor comprising the steps of:

• forming a semiconductor thin film containing microcrystals serving as crystal nuclei for polycrystallization on an insulating substrate, comprising the steps of:
• forming an amorphous semiconductor layer;
• and
• annealing the amorphous semiconductor layer by a laser beam having an energy density near a threshold value of crystallization, thereby forming the microcrystal nuclei;
• polycrystallizing the semiconductor thin film by laser annealing, thereby forming a polycrystalline semiconductor thin film;
• and
• forming a source region a drain region, and a channel region in the polycrystalline semiconductor thin film,
• wherein the semiconductor thin film, prior to being subjected to the polycrystallization process, contains a microcrystalline semiconductor layer containing the microcrystals and an amorphous semiconductor layer in contact with the microcrystalline semiconductor layer, the microcrystalline semiconductor layer lying beneath the entire amorphous layer.

A method for fabricating a thin-film transistor comprising the steps of:

• forming a semiconductor thin film containing microcrystals serving as crystal nuclei for polycrystallization on an insulating substrate, comprising the steps of
• forming an amorphous semiconductor layer, and
• annealing the amorphous semiconductor layer by a laser beam having an energy density near a threshold value of crystallization, thereby forming the microcrystal nuclei;
• polycrystallizing the semiconductor thin film by laser annealing, thereby forming a polycrystalline semiconductor thin film;
• and
• forming a source region a drain region, and a channel region in the polycrystalline semiconductor thin film,
• wherein the semiconductor thin film prior to being subjected to the polycrystallization process comprises:
• a microcrystalline semiconductor layer formed on the insulating substrate, which contains the microcrystals;
• and
• an amorphous semiconductor layer formed on the microcrystalline semiconductor layer so that the microcrystalline semiconductor layer is interposed between the insulating substrate and the amorphous semiconductor layer, and the microcrystalline semiconductor layer lies beneath the entire amorphous semiconductor layer.